Hi and welcome to Just Answer!The issue is that the trust is a separate legal entity and may not be named a beneficiary unless specifically named in the Will. So far - all assets owned by the decedent at the time of death are included into the estate.Based on your information - you are an executor of your mother's estate - and received that income as a nominee. Because distribution is reported to you personally - you need to attach to your tax return a letter with explanations - that you are acting as the executor of your mother's estate - and provide the tax ID of the estate. Then - you will include that distribution into the income tax return of the estate - and attach a copy of 1099R (because it is issued with a different tax ID).
There is another issue - because your mother had a living trust - as the executor of your mother's estate - you may make an Election To Treat a Qualified Revocable Trust as Part of an Estate.Here is the form - http://www.irs.gov/pub/irs-access/f8855_accessible.pdf.In this case - you will file a combined income tax return for the trust and for the estate - and will not need to file two separate tax returns. If you do so - on the tax return - form 1041 - http://www.irs.gov/pub/irs-pdf/f1041.pdf - you need to check the box in the header - "G Check here if the estate or filing trust made a section 645 election"